Crests: you have to collect the indicated number of Silver medals to get them:
Dark Sonic: 100
Fire Sonic: 105
Wind Sonic: 110
Characters: collect Fire Souls and unlock the corresponding character in Party mode:
Shadow: 30
Cream: 42
Silver: 87
Blaze: 105
Bonuses: collect Fire Souls and unlock the corresponding bonus in Party mode:
Aim! Big Crossbow: 6
Sink ‘Em! Pirate Ship: 12
Row! Canoe Race: 18
Reel! Battle Fishing: 24
Thrust! Bone Knight: 36
Cross! Balance Race: 48
Watch Out! Trap: 54
Put It Out! Big Fire: 60
World Bazaar: 69
Fly! Ptero-Rider: 78
Spin! Propeller Race: 96
Extreme mode: 114
Final X Adventure: 126